The present invention relates to a light shielding helmet which includes a helmet shell and one or more lens assemblies to be mounted on the shell.
The invention has been developed primarily for use in welding operations and will be described hereinafter with reference to that application. It will be appreciated, however, that the invention is not limited to that particular field of use and is also applicable to helmets used during cutting or grinding operations, in metal production, or other applications where an operator using the helmet is subjected to high intensity radiation and particle splatter (e.g., molten metal fragments).
Many welding helmets are known. A common helmet includes a shell with a fixed lens for protecting the eyes of a user during a welding operation. It is also known to use a filter lens which automatically darkens in response to high intensity light from the welding operation, thereby attenuating that light to avoid damage to the user's eyes. In another known arrangement, referred to as a "lift front" helmet, the filter lens is moveable between filtering and non-filtering positions, and must be manually toggled between the two positions by the user in response to the timing of the steps of the welding operation. It is also known to releasably mount a lens cartridge to a helmet, such as that manufactured and sold by Hornell Elektrooptic AB and designated the Speedglas.RTM. 9000 helmet.
As will be understood by those skilled in the welding industry, different lens sizes are used for different welding applications and according to personal preference. For example, lens sizes of 133.times.144 mm (5.times.4 in.) and 83.times.108 mm (2.times.4 in.) are commonly used in the United States and Australia. Each lens size usually requires a helmet shell having a specific configuration. As a result, helmet shells of multiple configurations must be made and stocked. This increases the expense of manufacture because different helmet configurations require different tooling, the expense of distribution because multiple helmet configurations must be stocked, and user expense because more than one helmet configuration is typically required to meet different applications. Also, storing and handling multiple helmets is often inconvenient to the user.
Conventional welding helmets also have other drawbacks. For example, with respect to welding helmets having lift-front style lens holders, the pivoting frame carrying the filter lens typically includes an overcenter spring and cam mechanism which functions to urge the frame toward its up (non-filtering) and down (filtering) positions. Different helmets use different mechanisms but most involve the use of numerous separate parts. This increases production and assembly costs.